Combustor and cap assemblies for combustors in a gas turbine

ABSTRACT

The cap assembly of a turbine combustor includes a plurality of burner tubes sealed against fuel nozzles extending in the tubes. These piston seals are coated with a high velocity oxygen fuel coating to extend their service life. The outer cap body assembly includes concentric seal rings each with cantilevered convex fingers circumferentially offset from one another to seal between the cap assembly casing and the inner liner. The cap assembly casing is provided with a plurality of holes at predetermined locations about the casing to minimize or eliminate response to combustion dynamics.

The present invention relates to combustors and cap assemblies for combustors having increased service life and particularly relates to combustors and cap assemblies therefor for converting combustors and cap assemblies having a predetermined life cycle to combustors and cap assemblies having extended life cycles.

BACKGROUND OF THE INVENTION

In gas turbines, a plurality of combustors are typically arranged in an annular array about the axis of the turbine. For example, in one known turbine, eighteen combustors are circumferentially spaced about the turbine axis. Each combustor combines fuel and compressor discharge air into an fuel/air mixture which is then combusted with the resulting gases expanded through the blades of the turbine whereby work is extracted from the turbine.

Combustors including cap assemblies are typically rated for a predetermined number of hours of operation before requiring service. For example, a cap assembly may be rated for 8,000 hours of operation before requiring servicing New versions of the cap assembly, however, are capable of extended hours of operation, e.g. 24,000 hours. This has led to an excess supply of cap assembly hardware having the lower rated hours of operation. These excess cap assemblies thus constitutes stranded assets since the lower rated cap assemblies would not be utilized in upgraded or providing new cap assemblies in new turbines. Accordingly, there has been a need to convert the lower rated cap assemblies which are otherwise stranded assets to the higher rated cap assemblies with extended hours of service whereby the lower rated cap assemblies can be utilized for turbine upgrades or provided in new turbines.

BRIEF DESCRIPTION OF THE INVENTION

In a preferred embodiment of the present invention there is provided a cap assembly for a turbine combustor comprising: a plurality of burner tubes; a fuel nozzle in each burner tube; and seals between the burner tubes and the fuel nozzles, each seal including a ring having a high velocity oxygen fuel coating on a surface thereof.

In a further preferred embodiment of the present invention there is provided a combustor comprising: a combustor liner; a cap assembly in part received within an end of the liner; a seal between the cap assembly part and said liner including pair of generally annular rings with each said ring having a plurality of spring fingers at circumferentially spaced locations thereabout, said rings being concentrically disposed relative to one another with the spring fingers of one ring circumferentially offset from the spring fingers of another ring enabling the spring fingers of each ring to register with gaps between the spring fingers of said another ring.

In another preferred embodiment of the present invention there is provided a cap assembly for a turbine combustor comprising: a plurality of burner tubes; a fuel nozzle in each burner tube; an outer body sleeve surrounding said plurality of burner tubes and having a plurality of openings sized and located to protect against onset of a mode of combustion dynamics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a combustor containing a cap assembly upgraded in accordance with a preferred embodiment of the present invention;

FIG. 2 is an enlarged end elevational view of the cap assembly for the combustor of FIG. 1;

FIG. 3 is a cross-sectional view through an axis of the cap assembly;

FIG. 4 is a fragmentary enlarged view of a seal between the burner tubes and fuel nozzles within the cap assembly;

FIG. 5 is an elevational view of a seal between the cap assembly and combustor liner in accordance with the prior art;

FIG. 6 is a similar view of a seal between the cap assembly and liner in accordance with a preferred embodiment of the present invention;

FIG. 7 is a cross-sectional view of the seal of FIG. 6 taken about on line 7-7 in FIG. 6;

FIG. 8 is a fragmentary enlarged end view in an axial direction of the seal of FIG. 6;

FIG. 9 is an enlarged fragmentary cross-sectional view of a flange of the cap assembly fitting into the forward casing of the combustor;

FIG. 10 is an axial view of the outer casing of the cap assembly; and

FIG. 11 is a side elevational view thereof.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, particularly to FIG. 1, there is illustrated a combustor generally designated 10 for a gas turbine. Combustor 10 includes a cap assembly generally designated 12 at a forward end of the combustor. As is conventional, combustor 10 includes a flow sleeve 14, a combustor liner 16 and a transition piece 18. Additionally, the cap assembly 12 includes a plurality of burner tubes 20 which form an annular array of tubes about the axis of the combustor and about a central fuel nozzle 22. Each burner tube 20 also houses a fuel nozzle 24 illustrated in FIG. 1. Typically, compressor discharge air is supplied to the burner tubes and fuel nozzle for mixing with fuel to enable combustion, the combustion gases flowing through the transition piece 18 into the turbine to extract work from the gases.

The burner tubes 20 typically have piston seals 28 for sealing about the burner tubes and to the fuel nozzle which is received within the burner tubes. Prior burner tube piston seals constituted a limiting factor in the service life of the cap assembly of the combustor. In accordance with a preferred embodiment of the present invention, to extend the service life of the cap assembly in this aspect of the invention, a high velocity oxygen fuel coating 30 is provided on each piston seal 28 to extend the service life of the piston seal. The material of the seal per se is conventional and may comprise HAST-X and the coating is identified FSX-414. The coating may be applied to a thickness of approximately 7-9 mils whereby superior wear properties are provided to the piston seal 28.

Referring now to FIGS. 3 and 5-8, there is provided an outer cap body assembly seal for sealing the cap assembly to the liner in a manner which will extend the life of the outer cap body assembly seal. Referring to FIG. 5, prior seals typically included a single annular seal, generally designated 32, having a plurality of segments 34 extending from a seal base 36 secured to the outer housing of the cap assembly. The segments 34 are thus cantilevered from the base 36 with gaps 38 therebetween. Service life for this seal constituted a limiting factor for the overall service life of the cap assembly. To extend the service life of the cap assembly, an outer cap body assembly seal in the form of a pair of concentric rings is provided. Particularly, and referring to FIGS. 6-8, the seal assembly, generally designated 39, includes a pair of concentric outer and inner rings 40 and 42 respectively. Each ring included a base 44 and 46 respectively secured to one another and to the outer casing of the cap assembly. Each ring includes a plurality of fingers 48, 50 respectively with gaps 52 and 54 respectively between the fingers. The concentrically arranged rings 40 and 42 are circumferentially offset relative to one another. Thus, the spring fingers of one ring circumferentially offset from the spring fingers of the other seal ring enable the spring fingers of each ring to register with the gaps between the spring fingers of the other seal ring. The offset double seal ring, as illustrated in FIG. 3, is secured to the outer casing 60 (FIG. 1) of the outer cap body assembly and extends in a forward direction from its securement to the outer cap body casing. Thus, the seal rings are convex and cantilevered in a forward direction and are biased against the interior surface of the liner 16 (FIG. 1) to provide a seal between the liner and the outer cap body assembly. As a consequence, the service life of the seal between the outer cap body assembly and the liner has been extended correspondingly to the uprated service life of new cap assemblies.

Referring to FIG. 9, a flange is provided on the cap assembly and the flange has a chamfer.

Referring now to FIGS. 10 and 11, there is illustrated an outer casing 60 for the cap assembly. It has been found that in certain turbines, the outer casing has limited service life due to its response to certain combustion dynamics within the combustor. That is, vibratory action of the casing may occur at frequencies deleterious to extended service life. Therefore to extend the service life of the casing, a plurality of holes or openings 62 are provided at predetermined locations about the casing. For example, as illustrated in FIGS. 10 and 11, the holes 62 are provided in pairs in quadrants of the casing. By providing these holes, the vibratory response of the casing to combustion dynamics is substantially minimized or eliminated thereby extending the service life of the casing.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 

1. A cap assembly for a turbine combustor comprising: a plurality of burner tubes; a fuel nozzle in each burner tube; and seals between the burner tubes and the fuel nozzles, each seal including a ring having a high velocity oxygen fuel coating on a surface thereof.
 2. A cap assembly according to claim 1 wherein said seal is formed of HAST-X.
 3. A combustor comprising: a combustor liner; a cap assembly in part received within an end of the liner; and a seal between the cap assembly and said liner including pair of generally annular rings, each said ring having a plurality of spring fingers at circumferentially spaced locations thereabout, said rings being concentrically disposed relative to one another with the spring fingers of one ring circumferentially offset from the spring fingers of another ring enabling the spring fingers of each ring to register with gaps between the spring fingers of said another ring.
 4. A combustor according to claim 3 wherein each ring has a margin along an edge thereof with the spring fingers cantilevered from said edge.
 5. A combustor according to claim 4 wherein the spring fingers are arcuate with each spring finger following the arcuate contour of registering portions of a pair of spring fingers of said another ring.
 6. A combustor according to claim 5 wherein the spring fingers are secured to a casing of the cap assembly, said spring fingers of an outermost ring having radially outward cantilevered convex portions for sealing about an inner surface of the liner.
 7. A combustor according to claim 6 wherein said radially outward convex portions have a high velocity oxygen fuel coating.
 8. A cap assembly for a turbine combustor comprising: a plurality of burner tubes; a fuel nozzle in each burner tube; an outer body sleeve surrounding said plurality of burner tubes and having a plurality of openings sized and located to protect against onset of a mode of combustion dynamics. 